The biaxially oriented polypropylene film is obtained by coextruding polypropylene particles into a sheet and then stretching in both directions. Due to the orientation of the stretched molecules, the film has good physical stability, mechanical strength, air tightness, high transparency and gloss, and is tough and wear resistant. It is the most widely used printing film at present, and the thickness is generally 20~ 40 μm, the most widely used is 20 μm. The main disadvantage of biaxially oriented polypropylene film is poor heat sealability, so it is generally used as the outer film of composite film. For example, it is ideal for moisture resistance, transparency, strength, stiffness and printability after being combined with polyethylene film. Contains dry foods. Since the surface of the biaxially oriented polypropylene film is non-polar, the crystallinity is high, and the surface free energy is low, the printing performance is poor, the adhesion to the ink and the adhesive is poor, and the surface is required before printing and compounding. deal with.